Stringed musical instruments such as guitars typically have a fixed bridge arranged between tuning pegs at the end of the neck of the guitar and string attachment devices on the body of the guitar, with sound being generated by plucking or strumming the strings. In order to produce a vibrato effect, a tremolo device can be provided on a guitar to simultaneously alter the tension of the strings during play. Fulcrum type tremolos tip or pivot to vary the tension on the instrument strings to produce the vibrato effect. Cam type tremolos rotate to vary the tension on the strings to produce a similar effect. Typically, a handle or bar is connected with the tremolo tailpiece to assist the player of the instrument with moving the tremolo bridge to produce the desired effect. The present invention relates to a cam tremolo device which can be switched between fixed and movable conditions.